In the prior grant period we investigated the hypothesis that persistent fetal microchimerism contributes to the pathogenesis of autoimmune disease. In studies of women with systemic sclerosis (SSc) we found that parous women had significantly greater levels of persistent fetal microchimerism compared to healthy parous controls. Fetal microchimerism was not uncommon, however, among healthy women. Fetal microchimerism was detected in immune competent peripheral blood cellular subsets in women with SSc and also in healthy women. The simple presence of persistent fetal cells is therefore not necessarily detrimental to the host. However, the hypothesis we proposed to test is that non-host cells contribute to autoimmune disease in the context of particular HLA alleles and HLA-relationships of host and donor cells. We found a nine-fold increased risk of SSc in women who had previously given birth to a child who was compatible for HLA-DRB1. Because cell traffic is bi-directional during pregnancy, and maternal cells can also persist in her progeny, women are uniquely potential recipients of microchimerism across generations. We found that HLA-DRB1 compatibility of the patient's mother from the perspective of her child was also associated with increased risk of SSc. T lymphocytes are implicated in the pathogenesis of SSc. Persistent fetal microchimerism among T lymphocytes was associated with specific HLA alleles of the mother and even more so of her child. Because significant findings were consistently greatest for the DRB1 locus, results point to the DRbeta1 molecule, and/or peptides derived from DRbeta1 as important to the interaction of host and non-host cells. The first aim of the current proposal is to define the role of HLA-relationships over three generations in risk of SSc in parous women. The second aim will evaluate familial HLA-relationships and HLA alleles in nulligravid women, children, and men who can also develop SSc. Specific Aim 3 studies will exploit Real-Time PCR techniques to quantitatively assess fetal microchimerism in the peripheral blood of parous women. Specific Aim 4 will quantitatively determine fetal microchimerism in immunologically active cellular subsets. Cell surface expression of candidate molecules that could interfere with maternal immune recognition will also be tested. Studies of Specific Aim 5 will provide a functional context from which to correlate results of prior aims. Artificial antigen presenting cells will be made and a T cell capture assay used to investigate T cells that respond to disease associated HLA-DR molecules/peptides. Women are disproportionately affected by autoimmune diseases. The current studies are designed to examine a long-term immunologic consequence of pregnancy. If, within the context of HLA-DRB1 compatible relationships and particular HLA alleles, persistent fetal microchimerism contributes to the pathogenesis of SSc, new therapies could be developed for this difficult disease.